What is vitamin A?
We will try to show here what foods are rich in vitamin a? Vitamin A is essential for normal vision, immune system function and embryonic development, skin growth and integrity, and bone formation. In addition, it is needed for the formation of ocular photoreceptors, to maintain the structure and integrity of the lining surface of the eyes and other mucous membranes. Vitamin A deficiency can lead to hemeralopia, eye damage and, in severe cases, even blindness. Acute or chronic excess of vitamin A can be toxic and lead to fetal pathology. A person is not able to produce vitamin A, he can only get it from food. A relatively stable concentration of the vitamin in the blood is maintained by a feedback mechanism that promotes its release from stores as needed, and also increases or decreases its absorption from food. Vitamin A deficiency mainly affects those who are malnourished and those who have a malabsorption syndrome – especially people suffering from celiac disease, cystic fibrosis, chronic pancreatitis, as well as the elderly and patients with alcoholism and liver diseases . The toxic effect of vitamin A is mainly due to the abuse of vitamin supplements. However, sometimes it is caused by a large amount of food containing high concentrations of vitamin A, such as liver.
Functions of vitamin A
Vitamin A is also essential for the visual, immune and reproductive systems, as well as bone health and gene regulation. In order for a child’s development to be successful, vitamin A is essential. The supplementation of vitamin A has been shown to reduce infant mortality by 24% in countries with low levels of vitamin A in the diet. Children with severe vitamin A deficiency may develop eye damage leading to blindness. Because of the proven beneficial properties of this micronutrient, researchers recommend providing supplements to children at risk of deficiency in vitamin A because of the recognized benefits of this micronutrient. One of the most important functions of vitamin A is to regulate the genetic expression of the differentiation process of cells. During development, cells can differentiate. This process allows the cell to become specialized, such as a muscle or nerve cell. However, the risk of vitamin A overdose does not seem to be related to pro-vitamin A carotenoids from food, as increased intake has been associated with a decreased risk of osteoporosis. In addition, the intake of provitamin A carotenoids has been linked to a reduced risk of cognitive decline and dementia in some studies which have been conducted.
How much vitamin A do I need?
For comparison, the term Retinol Activity Equivalent (RAE) was developed due to the different potencies of vitamin A and provitamin A carotenoids. As vitamin A levels in foods are measured in RAE, food labeling is simplified. There is an equal amount of RAE and retinol (active vitamin A) in one microgram. Two grams of beta-carotene in a supplement counts as one microgram of RAE. Carotene from plant sources, such as fruits and vegetables, corresponds to a much smaller amount of RAE. RAE is made up of 12 micrograms of beta-carotene or 24 micrograms of alpha-carotene. Recommendations for daily intake of retinol equivalent activity (RAE) depending on age and gender:
- Children from birth to six months of age: 400 µg RAE
- Children 7-12 months: 500 micrograms RAE
- Children 1-3 years old: 300 micrograms of RAE
- Children 4-8 years old: 400 micrograms of RAE
- Children aged 9-13 years old: 600 micrograms of RAE
- Women over 14 years of age: 700 micrograms of RAE
- Men over 14 years of age: 900 micrograms of RAE
- Girls aged 14-18 during pregnancy and breastfeeding: 750 and 1200 µg RAE
- Women 19-50 years old during pregnancy and breastfeeding: 770 and 1300 µg RAE
Vitamin A deficiency
As stated earlier, vitamin A plays a key role in child development, so deficiency can lead to increased susceptibility to infections, blindness, skin rashes and other developmental abnormalities. Low levels of vitamin A have also been shown to increase the risk of bone loss and osteoporosis.
Excess vitamin A
In rare cases, an excess of active forms of vitamin A can lead to death. However, cases of fatal overdose require a very high level of vitamin A intake. At lower intake levels, excess active forms of the vitamin are also associated with loss of bone mass, especially in people with vitamin D deficiency or those who are obese. Interestingly, provitamin A carotenoids do not appear to increase bone mass loss, and some studies suggest that they may even have a protective effect. A study in Japan showed that women with the highest levels of beta-carotene and beta-cryptoxanthin in their blood had a 76% and 93% lower risk of developing osteoporosis, respectively. As for carotenoids, an excess of provitamin A may give the skin an orange colour, but this poses no danger. When consumed in large quantities, carotenoids are deposited in the skin. Although this is not a very accurate way of testing, you can often get an idea of the level of carotenoid intake by the bright orange hue of the skin in the palms of your hands. Even at high intake levels, food-derived carotenoids appear to be quite safe.
Food sources of vitamin A
Numerous food sources provide vitamin A either as the active form of vitamin A or as pro-vitamin A carotenoids. Here, we will try to show what foods are rich in vitamin a
The active form of vitamin A
Active vitamin A, or retinol, is found in a number of animal products. Meat, eggs, seafood, poultry and dairy products contain the active form of vitamin A. Liver contains quite a lot of this vitamin, but cod liver oil is particularly rich in it.
Provitamin A carotenoids
In terms of obtaining vitamin A from beta-carotene and other provitamin A, carotenoid-rich foods are probably the safest source of vitamin A for two reasons. First, as mentioned earlier, there is a possibility of exceeding safe levels of retinol, or active vitamin A, in the body, but fortunately, food-derived provitamin A carotenoids do not appear to have a toxic threshold. While dietary carotenoids have been associated with significant health benefits, supplements with synthetic beta-carotene appear to carry some risks. A study involving smokers found an increased risk of cancer and death with synthetic beta-carotene supplements. However, diets high in beta-carotene from food have been shown to reduce the risk of heart disease and other chronic diseases. Although not proven, the problem with synthetic beta-carotene may be due to differences in the synthetic form compared to natural beta-carotene. Natural beta-carotene exists in two forms, while synthetic beta-carotene consists of only one. In general, the safest option is to include foods high in provitamin A carotenoids in your diet to avoid problems with synthetic beta-carotene supplements and consuming too much active vitamin A.
Food sources of provitamin A
what foods are rich in vitamin a? Dark orange to yellow coloured foods are often rich sources of provitamin A. Carrots, common and waxy pumpkin, sweet potatoes, apricots, cantaloupe, dark leafy greens, bell peppers, grapefruit and broccoli are excellent sources of pro-vitamin A carotenoids.
Superfoods are sources of vitamin A
Dark orange to yellow coloured foods are often rich sources of provitamin A. Carrots, common and waxy pumpkin, sweet potatoes, apricots, cantaloupe, dark leafy greens, bell peppers, grapefruit and broccoli are excellent sources of pro-vitamin A carotenoids. Superfoods are sources of vitamin A
A number of so-called superfoods are also rich in carotenoids. Red palm oil has extremely high levels of this substance. It contains 15 times more vitamin A than carrots and 44 times more than leafy greens. The dark red colour of the oil indicates high carotenoid content. Goji berries are another rich source of provitamin A. In Chinese phytotherapy these Asian-grown berries are often used for their rejuvenating properties. They are rich in carotenoids and contain about four times as much beta-carotene as carrots. They are also extremely rich in another potentially important carotenoid for eye health, zeaxanthin. Another plant in the same family as goji berries can be found in South America that is a good source of vitamin A. We are talking about golden berries, or physalis, a tart fruit with a golden orange colour, again indicative of its carotenoid content. Depending on the variety and growing conditions, physalis typically contain varying levels of beta-carotene, from the same amount found in carrots to ten times that amount. Like goji berries, physalis is very rich in zeaxanthin. Spirulina and chlorella, two edible algae, are also excellent sources of carotenoids. Spirulina contains 50 times more beta-carotene per unit weight than carrots. Chlorella contains slightly less, coming in a respectable second place. In addition, both types of algae are rich in other vitamins, minerals and protein.
Some common spices are also excellent sources of provitamin A. Paprika and cayenne pepper are rich in beta-carotene. Basil, parsley, marjoram and oregano also contain significant amounts. Spices are a simple way not only to make a dish tastier but also to fill it with nutrients.
Food sources of vitamin A
Vitamin A comes in two main forms: the active vitamin A, derived from animal products, and pro-vitamin A carotenoids, found in plants. Vitamin A is important for cell differentiation, immune, reproductive and visual system function, as well as bone health and gene regulation. Although it is possible to consume too much active vitamin A, pro-vitamin A carotenoids from food appear to be quite safe for our bodies. Studies show that they also have significant health benefits, including protection against heart disease, osteoporosis, other chronic diseases and dementia. Eating foods and superfoods rich in provitamin A appears to be an effective way to promote health. Here, we have showing what foods are rich in vitamin a?
Author: Dr Scott Busing
Dr Scott Busing is a naturopathic physician with more than fifteen years of experience in integrative medicine. Dr Scott Busing has helped numerous patients improve their health. Throughout his career, he has collaborated in a multidisciplinary partial hospitalisation programme for patients with mental illness, as well as treating people with chronic pain at the Integrative Pain Management Clinic in Southern California. For more information, visit buesingnaturopathic.com